Did you get a letter from the IRS that says you owe? What does it say exactly? Did they change something and dis-allow the childcare credit or child tax credit?
TurboTax does not receive any information from the IRS or your state after your return was filed, so no one at TurboTax knows about a letter you received from the IRS or the state.
(what the letters from the IRS mean)
I GOT A LETTER FROM THE IRS
I AM BEING AUDITED
If you purchased Audit Defense:
TurboTax has a special phone number for help with IRS/state tax letters, which will be easier than going through regular Customer Support. At the page below, click on the blue button that says "Get Help from TurboTax Support". Then it will ask you what tax year is your letter. Then it will ask you what the letter concerns. Then it will show you the phone number during posted business hours.
Turbotax never mails tax returns. If your return can't be e-filed, then you must print your return yourself, sign it in ink, and mail it to the IRS.
You will need to give us more information to help us understand your question, and you need to read the notice very carefully. "You did not mail a return and we think you owe tax" is a very different situation from "We have made changes to your tax return and now you owe."